Microwave ovens

Abstract: A microwave oven has a grill heater (20) mounted for pivotal movement between positions adjacent a side wall and the top wall of the cooking space (10) in the oven. Food on a rotating turntable (1) in the oven can thus be exposed around all its side or sides to the heater (20) in its side position.

Description: The present invention relates to a microwave oven, more particularly to a microwave oven having a grill heater. A typical modern microwave oven has two modes of operation. One is a general microwave oven cooking mode in which foods put in the inside of the cooking space are cooked by generated microwaves. The other is a grill mode in which foods put in the inside of the cooking space are cooked by the radiant or convected heat generated in a grill heater. GB-A-2165729 describes a combined microwave oven and grill oven. The grill heater is selectively movable about a pivotal axis towards the base of the oven. The oven may automatically select the position of the heater according to stored information. EP-A-0609138 has a priority date of 29th January 1993 and was published on 3rd August 1994. It also discloses a microwave oven which includes a rotatable heater. The heater is rotatable between a horizontal and a vertical orientation. It is mounted to one side only of the cooking chamber by connection means in the upper part of the chamber. The present invention is directed at a microwave oven having a grill heater, in which the heater is pivotally mounted. According to the invention, the heater is mounted for pivotal movement between a side wall and a top wall of the cooking space in the oven, and the ends of the heater are mounted in bearings proximate the junction between the side wall and the top wall of the cooking space in the oven. The grill heater in ovens of the invention will normally be adapted to overlay substantially the entire surface of a side wall of the cooking space, and be supported in bearings held in adjacent side walls. The heater can conveniently be mounted at the back of the cooking space. In all embodiments of the invention the preferred form of grill heater has a mid-portion with bent and projected portions forming an extended grill area to maximise the grill effect. Location of the grill heater at a side of the cooking space, in combination with a rotatable turntable, can achieve a more comprehensive grilling effect on a food product disposed in the oven. Where the grill heater is also pivotally mounted at one edge thereof, it is additionally made more accessible for cleaning. During grilling, the heater can become coated with products of the cooking process which can be difficult to remove, and by pivoting the heater away from an adjacent surface its cleaning can be greatly facilitated. Provision might also be made for the grill heater to be wholly demountable. The invention will now be described by way of example and with reference to the accompanying schematic drawings wherein: Figure 1 is a schematic sectional side view showing a grill heater in a microwave oven of known construction; Figure 2 is a sectional side view of a microwave oven in accordance with the present invention; Figure 3 is a sectional front view of the oven shown in Figure 2; Figure 4A is an exploded view of the left hand bearing for the grill heater of the microwave oven shown in Figure 3; Figure 4B is an exploded view of the right hand bearing for the grill heater of the microwave oven shown in Figure 3; Figure 5 shows a portion from Figure 3, but to an enlarged scale; Figure 6A is a partial sectional view of an alternative form of left hand bearing for the grill heater of the oven shown in Figure 3; Figure 6B is a partial sectional view of an alternative form of right hand bearing for the grill heater of the oven shown in Figure 3; Figure 7A is a perspective view of the bushing in the bearing of Figure 6A; and Figure 7B is an exploded perspective view of the bushing in the bearing of Figure 6B. Figure 1 shows a microwave oven with a grill facility for roasting foods. As shown in Figure 1, a grill heater 3 is mounted at the upper wall or ceiling of a cooking space 2 in which a turntable 1 is fitted. The grill heater 3 is fixed in the hole formed in the adjacent side wall of the cooking space 2. For grilling or roasting, food is first placed on a supporting box 4 on the turntable 1. After that, as power is supplied and one selects the mode for operating the grill heater, so, the grill heater 3 starts to generate heat. The food (fish is illustrated) on the supporting box 4 is grilled or roasted by heat generated by the grill heater 3, and is homogeneously cooked by the rotation of the turntable 1. The conventional microwave oven shown in Figure 1 has the disadvantage that the supporting box is needed to roast foods such as fish, meat etc. because the grill heater 3 is fixed at the upper portion of the cooking room 2. In addition, because only one side of the food on the supporting box is exposed to heat from the grill heater 3 and the other side is not, the food must be turned midway through the cooking process. Further, cleaning of the grill heater is inconvenient because oil generated by the cooking process becomes attached on the rear side of the grill heater 3. In the microwave oven shown in Figures 2 and 3, the grill heater 2 is pivotally mounted in the cooking space 2. The heater can be pivoted to a vertical orientation so as to cook the side or the reverse of a food which does not receive the generated heat directly from a ceiling located heater. The grill heater 20 has a shape which the mid-portion of it is bent and is projected, and both ends of it are respectively connected to the side walls of the cooking room 10. In order to control the orientation of the grill heater and prevent the horizontal rock of the connected grill heater, left and right bearings 30, 40 are provided. As shown in Figure 4A, the left hand bearing 30 comprises a bushing 31 which receives the ends of two grill heater elements 20 through two holes. The bushing 31 rotates with the grill heater 20. A fixed cylindrical ring 32 and a stopper 33 are provided for rotating the grill heater 20 with the connected bushing 31 to a desired angle, together with a bracket 34 for defining the rotary angle of the stopper 33 and restricting undesired movement of the heater 20. As shown in Figure 4B, the bearing 40 positioned in the right side wall of the cooking space 10, comprises a bushing 41 which receives the other ends of two grill heater elements 20. A rotary ring 42 receives the bushing 41 and a small cylindrical part of it is inserted in the right hole of the cooking space 10 from the outside of the wall of the cooking space 10. A circular holding member 42a and a bracket 44 are provided for preventing the rotary ring 42 inserted at the right hole of the cooking space 10 from coming out the outside of the cooking space 10. The bushing 41 and the rotary ring 42 are joined by a pin 43 through holes 41a, 42b. When the grill heater 20 is not used, it is moved toward the inner or upper wall by rotating the stopper 33, so that the cooking space 10 is broad. In order to roast a food on the turntable, the knob 33a of the stopper 333 is turned to the desired position, and the grill heater 20, the bushing 31 and the stopper 33 of the left bearing 30 all rotate together. At the same time as the rotation of the left bearing, the bushing 41 and the rotary ring 42 of the right bearing 40 also turn. At this time, the rock in the horizontal direction is prevented by the bracket 34, 44 and the circular holding members 31a, 42a. Figures 6 and 7 are partial sectional view and perspective view of alternative bearings in accordance with the present invention. As shown in the drawings, a left bearing 50 positioned at the wall of the cooking space 10, comprises a bushing 51 having a circular holding member 51b for preventing the bushing inserted at the left hold of the cooking space 10 from coming out the left wall of the cooking space 10. A stop ring 53 inserted to the cylinder of said bushing 51 is fixed at the wall of the cooking space 10 and a stop plate 54 is held against the bushing by a screw 52. In order to join the stop plate 54 to the bushing 51, holes are formed in the sectional face thereof and the face of the stop plate 54. The hole 51a of the bushing 51 is shown in Figure 7A. The hole in the stop ring is not shown in the drawings. The right bearing 60 of Figures 6B and 7B comprises a bushing 61 in which the right ends of the two grill heater elements 20 are inserted, and a further bushing 62 in which said bushing 61 is inserted. The bushing 62 is joined with the bushing 61 from the inside of the cooking space 10 through the hole of the cooking space 10 and it has a circular holding member 62a for preventing the bushing 62 inserted at the right hole of the cooking space 10 from coming out. A groove 62c with an E-ring 63 prevents the inserted bushing 62 from coming out of the right wall of the cooking space 10. A screw 64 joins the bushing 62 with the bushing 61 through each of holes 62b, 61a. When a user roasts a food on the turntable using the microwave oven of the present invention, he can rotate a projection part of the grill heater 20 to an appropriate position for cooking using the stop plate 54 or the grill heater itself.

Claims: A microwave oven having a grill heater (20), in which the heater is pivotally mounted, characterised in that the heater (20) is mounted for pivotal movement between a side wall and a top wall of the cooking space (10) in the oven, and the ends of the heater (20) are mounted in bearings (30, 40) proximate the junction between the side wall and the top wall of the cooking space (10) in the oven. A microwave oven according to Claim 1 wherein one of the bearings (30, 40) includes means for controlling the pivotal position of the grill heater (20). A microwave oven according to Claim 2 wherein said one bearing comprises a bushing (31) in which one end of the grill heater is received, and including a holding member (31 a) for retaining the bushing in the oven wall; a sleeve (32) receiving the bushing (31) and fixed in the wall of the cooking space (10) in the oven; and a stopper (33) secured to the bushing (31), for controlling the pivotal position of the grill heater (20). A microwave oven according to Claim 3 wherein said one bearing includes a bracket (34) for defining the pivotal position thereof. A microwave oven according to any of Claims 2 to 4 wherein said other of the bearings comprises a bushing (41) in which the other ends of the grill heater are received, a sleeve (42) receiving the bushing (31), and being rotatable with the bushing in a wall of the oven, with a holding member (42a), and a bracket engaging the rotary ring, for preventing horizontal movement of the bearing. A microwave oven according to any of Claims 2 to 4 wherein the second bearing comprises a first bushing (61) receiving one end of the grill heater (20), a second bushing (62) receiving the first bushing, having a circular holding member (62a) engaging the inside of the wall of the cooking space (10), and forming a groove aligned with said wall; and a securing ring (63) in the groove and engaging the outside of said wall to hold the second bushing (62) thereagainst. A microwave oven according to any preceding Claim wherein the grill heater (2, 20) includes a mid-portion which is bent and projected. A microwave oven according to any preceding claim including a turntable (1) for supporting food in the cooking space (10), and means for rotating the turntable (1) to successively expose all sides of such food to the grill heater (2, 20) when the heater is located adjacent the side wall of the cooking space (10).

Inventors: KWON CHUI-HO, KWON, CHUI-HO
Applicants: LG ELECTRONICS INC, LG ELECTRONICS INC.
Application year: 1994
Main classification: H05B6
IPC codes: F24C7, H05B6